Homework Help:
Force exerted by an external electric field

1. The problem statement, all variables and given/known data
A particle of mass 1.20 kg with a charge of +2.30 mC is shot into a region with an electric field of strength 18.0 N/C, having a direction opposite the particle's velocity. If the particle has an initial speed of 2.40 m/s, how long does it take to come to a complete (though momentary) standstill? Assume there are no other forces acting on the particle.

2. Relevant equations
F = qE
F= ma

3. The attempt at a solution
I'm not sure what equation to start with because of all the information already given. I couldn't find any equations dealing with time in the chapter this problem was in. It sounds like you may have to use kinematics but I'm not sure if that is the correct way to do it.